Commit 2f59e1eb authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

net: Add flow_keys digest 



Some users of flow keys (well just sch_choke now) need to pass
flow_keys in skbuff cb, and use them for exact comparisons of flows
so that skb->hash is not sufficient. In order to increase size of
the flow_keys structure, we introduce another structure for
the purpose of passing flow keys in skbuff cb. We limit this structure
to sixteen bytes, and we will technically treat this as a digest of
flow_keys struct hence its name flow_keys_digest. In the first
incaranation we just copy the flow_keys structure up to 16 bytes--
this is the same information previously passed in the cb. In the
future, we'll adapt this for larger flow_keys and could use something
like SHA-1 over the whole flow_keys to improve the quality of the
digest.

Signed-off-by: default avatarTom Herbert <tom@herbertland.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ada1dba0

include/net/flow_keys.h

+16 −0
Original line number Diff line number Diff line
@@ -42,4 +42,20 @@ static inline __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 
u32 flow_hash_from_keys(struct flow_keys *keys);

unsigned int flow_get_hlen(const unsigned char *data, unsigned int max_len,

			   __be16 protocol);



/* struct flow_keys_digest:

 *

 * This structure is used to hold a digest of the full flow keys. This is a

 * larger "hash" of a flow to allow definitively matching specific flows where

 * the 32 bit skb->hash is not large enough. The size is limited to 16 bytes so

 * that it can by used in CB of skb (see sch_choke for an example).

 */

#define FLOW_KEYS_DIGEST_LEN	16

struct flow_keys_digest {

	u8	data[FLOW_KEYS_DIGEST_LEN];

};



void make_flow_keys_digest(struct flow_keys_digest *digest,

			   const struct flow_keys *flow);



#endif

net/core/flow_dissector.c

+27 −0
Original line number Diff line number Diff line
@@ -310,6 +310,33 @@ static inline u32 ___skb_get_hash(const struct sk_buff *skb, 
	return __flow_hash_from_keys(keys, keyval);

}



struct _flow_keys_digest_data {

	__be16	n_proto;

	u8	ip_proto;

	u8	padding;

	__be32	ports;

	__be32	src;

	__be32	dst;

};



void make_flow_keys_digest(struct flow_keys_digest *digest,

			   const struct flow_keys *flow)

{

	struct _flow_keys_digest_data *data =

	    (struct _flow_keys_digest_data *)digest;



	BUILD_BUG_ON(sizeof(*data) > sizeof(*digest));



	memset(digest, 0, sizeof(*digest));



	data->n_proto = flow->n_proto;

	data->ip_proto = flow->ip_proto;

	data->ports = flow->ports;

	data->src = flow->src;

	data->dst = flow->dst;

}

EXPORT_SYMBOL(make_flow_keys_digest);



/*

 * __skb_get_hash: calculate a flow hash based on src/dst addresses

 * and src/dst port numbers.  Sets hash in skb to non-zero hash value

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